furnace problems

ok so this damn furnace is giving me more problems. it is a goodman gmpn-120-5. at the begining of the winter the heat would not kick on and after alot of trouble shooting, and help from you guys i determined it was the board. replaced it and everything was good until a couple of weeks ago when the fan would keep kicking on and off,, it would do this for sometimes a half an hour but eventually kick on. i figured it was te run cap so i replace it on friday and everything was fine until just about 2 hours ago i realized it was getting cold in the house and went to check on the furnace and the blower fan starts, the igniter comes on, gas valve opens and ignites the burners, but the main fan never kicks on so the system shuts down and retries with the same results. the LED on the board never does flash with any error sequence, so what could be the problem this time?

The board itself is usually marked with "Heat" which would be the terminal to test for the 120V to the fan but the fact that the board led is not showing a limit code is odd.
I would jumper the R & W stat connection points inside the furnace (with the stat lines removed) to eliminate a stat circuit problem.
And I'd be checking that all the ground wires within the furnace are tightly connected.

ok so i didnt get a chance to mess with this last night, so i just went down to see if the board was sending 120 to the fan, and it did and the fan started right up. i think i found what is causing the problem. there is water running down and dripping on the control board. i will do my best to describe where the water is coming from. if you are looking at the furnace there is the small blower fan that connects to the pvc pipe that runs outside. that blower is connected to a black cover the width of the furnace, and roughly 8" tall, this cover has screws all the way around it i am guessing to allow replacement. the water is coming out at the bottom of it.

Your drainage is clogged. Kill Power. Remove trap, clean in sink with bleach and warm soapy water. Rinse thoroughly. Also clean all hoses in the same way. Mold builds up in condensate lines, Also check your intake and exhaust lines and make sure they are clear. Usually 3 inch PVC in HE condensing furnaces. When you put the trap back, prime it before connecting hoses.

Good luck.

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